Physical models of vascular systems are being used extensively in our laboratory to study a variety of hemodynamic phenomena. During the past year, the major effort has been directed to projects in the following two categories: hemodynamic studies related to the development of turbulence during pulsatile flow, and intra-arterial infusions of radiation-sensitizing drugs into the uterine artery for the treatment of cervical cancer. (1) The onset of turbulence during oscillating flow has been studied in a series of straight, rigid tubes. An empirical correlation was developed that would predict the transition from laminar to turbulent flow as a function of the peak flow (Reynolds number), the frequency of oscillation (Womersley parameter), and the stroke volume (Strouhal number). Similar experiments were performed with branched tubes of two different area ratios, in models of pig coronaries, and in models of stenoses. Turbulence correlations, friction factor calculations, and velocity profile data were derived for these configurations. (2) A glass model of the human cervical artery system was fabricated, based on anatomical illustrations of the geometry. The model has been connected to a flow circuit, and the proper flow rates and wave forms for ileofemoral and cervical flows have been established. The system is being prepared for studies of dye injections into the various branch arteries via intraarterial catheter, to assess the distribution of injectate into the various arterial regions both visually and quantitatively.